This invention relates to a power load survey apparatus comprising an electronic power sensor, a collector cartridge for data collection, and a memory/magnetic tape converting device.
Conventional power load survey apparatuses have generally comprised a power load survey meter 1 and a cassette recorder 20 as shown in FIGS. 1A and 1B.
The mentioned power load survey meter 1 operates to gauge a power load amount per limited time length and store the gauged amount in a memory, and to provide output data of the gauged amount with an ID number added to identify the instrument from which the load power was gauged. The mentioned cassette recorder 20 is normally not connected to the power load survey apparatus 1, but only when the mentioned output data is desired to be collected. After the cassette recorder 20 has collected the output data, the recorder is removed from the load survey apparatus 1 and connected to a separate magnetic cassette tape and magnetic tape converting device (not shown) where the data is transferred to a magnetic tape for computers. Thus, the output data on the magnetic tape can be tabulated and printed by a separately provided computer.
The conventional power load survey meter 1 has voltage and current converters 2 and 3 for converting an input load voltage VL and load current IL to signals proportional to the load voltage and the load current, respectively. Multiplier 4 multiplies the signals from both converters with each other. An integrator 5 including a W/F converter integrates the multiplication values. The integrated power value is frequency divided by a frequency divider 6, and the divided signals are counted by a counter 7. Memory 9 stores the count value therein in accordance with control of a control circuit 12. A timer circuit 8 for determining a time length and an ID number setting circuit 11 for setting a number identifying the instrument from which the input data are collected are provided. Outputs from both circuits are stored in the memory 9 under control of the control circuit 12. An output circuit 10 controls and outputs the data stored in memory 9 therefrom under control of the control circuit 9. An electric source 13 for the component circuits included in the power load survey meter 1 is formed from the mentioned load voltage VL.
The cassette recorder 20 includes an input circuit 21 for receiving the output data from the mentioned output circuit 10 when the recorder 20 is connected to the power load survey meter 1. A magnetic cassette tape device 22 records the signals received in the input circuit 21. The recording operation is performed under control of control circuit 23 which is in turn controlled by command from an operating section 24. Time data from the time keeping circuit 25 to indicate the time that the recording was made on the magnetic cassette tape device in terms of year, month, day, hour, minute and second. A setting time display section 26 sets the time of the time keeping circuit 25 and displays the time. The cassette recorder 20 has a power source 27 for supplying supply voltage to the component circuits.
The above outlined power load survey apparatus permits recognition of the instrument ID numbers, collected data and time of recording of the collected data on the basis of the data recorded in the magnetic cassette tape device 22 in the cassette recorder 20, thereby allowing the data to be analyzed in various ways by a computer per key-coded instrument ID number.
In use of the conventional power load survey apparatus, power load amounts are measured by power load survey meters 1 installed on the premises of individual consumers and collected from time to time by the mentioned cassette recorder. One or two cassette recorders 20 are sufficient to cover about 100 power load survey meters 1. Use of a magnetic cassette tape for storing data, however, has the following problems.
1. The operable temperature range of magnetic cassette tape is narrow so that use thereof is inhibited in cold or hot locations.
2. A portable cassette recorder 20 consumes much power requiring frequent replacement of the battery cells which are the power source.
3. Recording of data is performed with the magnetic cassette tape running, taking a long time.
4. The cassette recorder comprising the magnetic cassette tape device 22, battery cells 27 and control circuit 23 is heavy which makes it difficult to carry.
5. The time keeping circuit 25 contained in the cassette recorder 20 is subject to errors after a long period of use, which have to be rectified. The problem is worsened when the number of subscribers increases so that hundreds of cassette tape recorders have to be used. Operators then have to tune the individual time keeping circuits to a broadcasting time tone, making it difficult to tune all the time keeping circuits exactly.
In an attempt to overcome the enumerated problems and drawbacks, power load survey meters and cassette recorders have been integrated and only the magnetic cassette tape replaced. This prior art attempt solved the second, third and fourth problems, but could not solve the first and fifth ones, leaving the power load survey meters larger and more expensive.